1998 Jeep Cherokee Wont start

The lights and windows will work with a bad battery, but for the starter, you'll usually hear at least some type of clicking from the starter relay or the solenoid on the starter motor. Measure the battery voltage. It should be 12.6 volts if it's good and fully-charged. If you find close to 12.2 volts, it's good but discharged. If it's around 11 volts it has a shorted cell and must be replaced.

Do you hear a single, rather loud clunk from the starter solenoid each time you turn the ignition switch to "crank"? If not, feel the starter relay to see if it's clicking when a helper turns the ignition switch to "crank". If it's not, the system can be broken down into four circuits, and each one has a test point in the starter relay socket. The most common suspect is the neutral safety switch. Often the starter will work if you try it in neutral instead of park.

If that's a very faint, light click, that could be any of a number of unrelated relays turning on or off. You'll need to place your finger on them when a helper turns the ignition switch to "crank" to feel if the starter relay is clicking.

That loud clunk from the starter solenoid is WAY louder than any relay, and you'll be able to hear that from across a small parking lot. This is a real common problem on the little silver Nippendenso starters caused by burned-away contacts in the solenoid, but you don't have that style. You could have a bad solenoid too, but on yours that isn't common.

To be sure we're looking at the right things, use a test light or voltmeter to measure the voltages on the starter terminals. First measure on the smaller solenoid terminal. If you get 12 volts there when your helper turns the ignition switch to "crank", the neutral safety switch and starter relay are working. The loud clunk means the solenoid is engaging.

Next, measure the voltage on the larger solenoid terminal the battery positive cable is attached to. You'll find full battery voltage there, a little over 12 volts. We need to see what that voltage goes to when trying to crank the engine. Typically battery voltage, and the voltage at that starter terminal, will drop to around 10 or 11 volts, but with your failure to crank, it should remain near 12 volts. If it drops to close to 0.0 volts, that cable has a bad connection.

If you still find 12 volts on the large terminal when the solenoid is engaged, measure on the other one where the fat braided wire goes into the starter motor. If that one is 0.0 volts, the solenoid is defective.